Interpretive Summary: Flowering and kousa dogwoods are ornamental trees valued for their four season appeal and for their importance to retail and wholesale nurseries. While most flowering dogwood cultivars are susceptible to two major diseases, anthracnose and powdery mildew, resistance to both of these diseases has been found in kousa dogwood. This study was conducted as a preliminary step in using kousa dogwood for improving flowering dogwood through breeding. Because both flowering and kousa dogwood do not self-pollinate, honeybees can be used to pollinate them. Dogwood plants, both of the same species and of different species, were placed into individual insect-proof cages into which honeybees were introduced. Seeds were produced and determined to be hybrids using molecular markers. While hand-pollinations of dogwood are very time-consuming, honeybees can make large numbers of pollinations with minimal human labor requirements. This study provides the framework for conducting honeybee-mediated breeding work in flowering and kousa dogwood.

Technical Abstract:
Flowering (Cornus florida) and kousa (C. kousa) dogwoods are ornamental trees valued for their four season appeal and for their importance to retail and wholesale nurseries. The popularity of kousa dogwood has increased in recent years due to its resistance to dogwood anthracnose and powdery mildew as compared to flowering dogwood. This resistance allows the development of intra- and inter-specific cultivars with multiple disease resistance or a combination of disease resistance and specific ornamental traits. We have capitalized on the self-incompatible nature of dogwood to perform self and cross pollinations of flowering and kousa dogwood using honeybees. Self pollinations were conducted in 2006 and 2007 with C. florida ‘Appalachian Spring’ and ‘Cherokee Brave’ and with C. kousa ‘Blue Shadow’ and ‘Galilean’. The flowering dogwood self pollinations resulted in no seed production, whereas the kousa dogwood self pollinations resulted in low seed production, indicating self-incompatibility. Intra- and inter-specific crosses of flowering and kousa dogwood cultivars and breeding lines were conducted from 2006 to 2008. Honeybees were effective in facilitating seed production for all intra-specific crosses conducted. Seedling phenotypes of putative intra- and inter-specific hybrids are similar and practically indistinguishable, so dogwood specific simple sequence repeats were used to verify a sample of the putative hybrids. The results demonstrated that honeybees were effective in performing controlled pollinations and that honeybee-mediated pollinations provide an alternative to time consuming hand pollinations for flowering and kousa dogwood.